These studies are designed to ascertain the effect of aging on hypothalamic-hypophyseal secretion of the antidiuretic hormone, arginine vasopressin (AVP), in response to: 1) overnight dehydration, 2) hypertonic saline infusion and 3) intravenous ethanol infusion. From such studies mechanisms of aging changes will be described and some of the clinical problems in salt and water conservation in aging individuals may be explained.